The present invention relates to a flat panel display of the modular guided beam type, and particularly to such a display in which the contact between the support walls and phosphor screen is minimized and good support for a shadow mask is provided.
There has been developed a flat display device which includes an evacuated envelope having substantially flat, spaced front and back walls and spaced, parallel support walls extending between the front and back walls. The support walls form a plurality of parallel channels extending across the front and back walls. A gun structure extends across one end of the channels and is adapted to generate electrons and direct the electrons as beams into the channels. In each of the channels is at least one beam guide which confines the electrons in the beam as the beam flows along the channels but which permits the beam to be deflected toward a phosphor screen on the surface of the front wall at a plurality of points along the channel. Such a display device is described in the copending application for U.S. Patent of T. O. Stanley, Ser. No. 607,492, filed Aug. 25, 1975 now U.S. Pat. No. 4,031,427, entitled "Flat Cathode Ray Tube". This type of display device will be generally referred to as a "guided beam display device".
In the copending application for U.S. Letters Patent of C. H. Anderson et al., Ser. No. 615,353, filed Sept. 22, 1975, now U.S. Pat. No. 4,028,582 entitled "Guided Beam Flat Display Device" there is shown and described a type of the guided beam flat display device in which at each point that the beams are deflected out of their focusing guides toward the phosphor screen the beams in each channel are simultaneously deflected transversely across their respective channels to scan the screen across the entire lateral dimension of the channels. This display device includes two spaced parallel grids between the focusing guides and the phosphor screen, one of the grids is for focusing the cross sectional area of the beams and the other grid is for accelerating the beam toward the phosphor screen. This type of the guided beam display device will be referred to as a "modular guided beam display device". For a color modular guided beam display device there are three beams in each channel and a shadow mask extends across each channel adjacent the phosphor screen.
One problem with the modular guided beam display device is that the area of contact between the support walls and the phosphor screen on the front wall must be minimized so that the support walls do not obscure too much of the phosphor screen. For this purpose it would be desirable to have the support walls as thin as possible. However, the thickness of the support walls, which are typically of glass, is limited in order that they will provide the necessary support against the atmospheric pressure loading. The support walls cannot be made entirely of metal because of electrical isolation requirements within the evacuated envelope. Therefore, it is desirable to have a structure which will provide the necessary support within the envelope and have a minimized width, and hence, area of contact with the phosphor screen.
Another requirement in the modular guided beam flat display device is with regard to the shadow mask. It is desirable that the device be of a structure which provides for ease of mounting the shadow mask in the envelope at the proper distance from the phosphor screen and be held with great precision laterally with respect to the screen.